Methods for casting a motor end shield

ABSTRACT

A cast end shield includes an opening extending therethrough and an insert at least partially embedded within the end shield at the opening. The end shield also includes a plurality of slots extending to the insert. In one embodiment, the insert is a substantially circular steel insert ring concentric with the opening and oriented such that an inner diameter of the insert ring is exposed from the end shield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/568,737 filed May 11, 2000 now U.S. Pat. No. 6,380,645, and assignedto assignee of the present invention.

BACKGROUND OF THE INVENTION

This invention relates generally to motor end shields, and, moreparticularly, to cast motor end shields including an insert and a methodfor casting the end shields.

Motors typically include a housing connecting two end shields, each endshield having an opening therethrough. The housing and end shieldssurround a stator core having a bore therethrough. A rotor, including arotor core and a rotor shaft, extend through the stator bore. The rotorshaft extends through the end shield openings. A bearing, positioned ateach end shield opening, contacts the rotor shaft and an inner diametersurface of each end shield. If the inner diameter surface is notproperly sized, shaped, and oriented, excessive noise, vibration, andwear may result.

Typically, cast end shields (for example, fabricated from aluminum),include a steel insert ring for contacting the bearings. The insert ringis positioned by a mold utilized to cast the end shield. Typically themold includes a protrusion on one half of a cope and drag castingpattern. The final location of the insert in the casting is a result ofthe inner diameter tolerance of the insert and the tolerance of thetapered protrusion. Thus, proper placement and orientation of the insertring is difficult.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment, a cast end shield includes an insert ringand three slots extending to the insert ring. The end shield alsoincludes an opening extending therethrough and the insert ring isoriented at the opening such that an inner diameter of the insert ringis exposed by the opening. The insert ring is a substantially circularsteel insert ring concentric with the opening.

A method of fabricating the end shield includes providing a moldcomprising a center axis, a rotor projection coaxial with the axis, anda plurality of orienting projections extending from the rotorprojection. The insert is oriented around the rotor projection such thatthe insert contacts the orienting projections. The end shield is castsuch that the insert is embedded within the end shield and an innerdiameter surface of the insert ring is exposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a motor including a cast end shield havingan insert ring therein;

FIG. 2 is a perspective view of one of the end shields shown in FIG. 1;

FIG. 3 is a cross sectional view of the end shield shown in FIG. 1 alongline 3—3; and

FIG. 4 is a perspective view of an exemplary mold bottom portionutilized to cast the end shield shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view of an electric motor 100 including a housing102, a first end shield 104 and a second end shield 106. End shields 104and 106 are connected to a pair of ends 108, 110, respectively, ofhousing 102. Motor 100 also includes a stator core (not shown) enclosedby housing 102 and end shields 104, 106. The stator core includes a bore(not shown) therethrough. A rotor (not shown) including a rotor core(not shown) and a rotor shaft 112 extend through the stator bore. Endshields 104 and 106 each include an opening (not shown) through whichrotor shaft 112 extends. Motor 100 further includes an axis 114 thatextends through rotor shaft 112 and the end shield openings. Rotor shaft112 is held in place within the end shield openings by two sets ofbearings (not shown). One set of bearings contacts end shield 104 androtor shaft 112 and a second set of bearings contacts end shield 106 androtor shaft 112.

FIG. 2 is a perspective view of a motor end shield, such as motor endshield 106 shown in FIG. 1. In one embodiment, end shield 106 isfabricated from cast aluminum. In alternative embodiments, end shield106 is fabricated from other metals that have the characteristics soughtfor end shield 106. End shield 106 includes an opening 120 extendingtherethrough. End shield 106 also includes a first ledge 122, a secondledge 124, and a third ledge 126. An insert 128 is at least partiallyembedded within end shield 106. In one embodiment, insert 128 is asubstantially circular steel insert ring concentric with opening 120.Insert 128 includes an inner diameter 130 that is fully exposed from endshield 106. In an alternative embodiment, insert inner diameter 130 ispartially exposed from end shield 106.

A plurality of slots 132 extend into second ledge 124 such that theyextend to insert 128 and expose a portion of insert 128. In oneembodiment, end shield 106 includes three slots 132 extending intosecond ledge 124 and evenly spaced around opening 120. In an alternativeembodiment, end shield 106 includes two slots 132 extending into secondledge 124 and evenly spaced around opening 120. In a further alternativeembodiment, end shield 106 includes four or more slots 132 extendinginto second ledge 124 and evenly spaced around opening 120. In a furtheralternative embodiment, slots 132 are not evenly spaced around opening120.

End shield 106 also includes a groove 134 extending around third ledge126. A rim 136 is adjacent groove 134 and extends to an outer perimeter138 of end shield 106.

FIG. 3 is a cross sectional view of end shield 106. End shield 106includes a center axis 140. Opening 120 is coaxial with axis 140. Insert128 is embedded within end shield 106 such that inner diameter 130 isexposed from end shield 106. A set of bearings (not shown) contactsinsert inner diameter 130. A machined groove 142 extends between secondledge 124 and insert 128. Machined groove 142 is configured to retain asnap ring (not shown) for maintaining the set of bearings positioned atinsert 128.

FIG. 4 is a perspective view of an exemplary bottom mold portion 150 forcasting end shield 106 (shown in FIGS. 1-3). Mold portion 150 includesan axis 152, a first projection 154 coaxial with axis 152, a secondprojection 156 coaxial with first projection 154, and a plurality ofthird projections 158 extending from first projection 154. In oneembodiment, mold portion 150 includes three third projections 158 whichextend radially outward from first projection 154. In a furtherembodiment, mold portion 150 is fabricated from sand. Mold portion 150further includes a ridge 160 that extends around second projection 156.

A method for fabricating a part, such as motor end shield 106 (shown inFIGS. 1-3), with an insert, such as insert 128 (shown in FIGS. 1-3)embedded at least partially therein includes the step of providing amold portion 150 including a center axis 152, a first projection 154coaxial with axis 152, and a plurality of third projections 158extending from first projection 154. Third projections 158 extendradially outward from first projection 154.

Insert 128 is oriented around first projection 154 such that insert 128contacts third projections 158. In one embodiment, insert 128 rests on atop surface 162 of third projections 158. Mold portion 150 is thenassembled with a second mold portion (not shown) such that a cavity isformed with insert 128 contained therein. A liquid cast material is thenintroduced into the mold cavity. In one embodiment, the cast material isaluminum. In alternative embodiments, the cast material is another metalsuitable for use as an end shield.

End shield 106 is cast such that the insert is embedded at leastpartially within said part. In one embodiment, insert 128 is asubstantially circular steel insert ring which is oriented such that thering contacts third projections 158. End shield 106 is cast such thatinner diameter 130 of insert 128 is exposed from end shield 106 afterend shield 106 has been cast. Opening 120 is machined to provide asmooth inner surface for the bearing to contact. In addition, a snapring groove (not shown) is machined adjacent insert 128 to provide alocation for a snap ring to retain the bearing in contact with insert128.

The above described end shield is fabricated with an embedded insertring that is precisely oriented prior to casting of the end shield. Theproper orientation of the inset prior to casting decreases machiningcosts and increases the longevity of the end shield.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit scope of theclaims.

What is claimed is:
 1. A method for fabricating a part with an insertembedded at least partially therein, said method comprising the stepsof: providing a mold comprising a center axis, a first projectioncoaxial with the axis, and a plurality of second projections extendingfrom the first projection, the second projections extending radiallyoutward from the first projection; orienting the insert around the firstprojection of the mold such that the insert contacts the secondprojections of the mold; and casting the part such that the insert isembedded at least partially within said part.
 2. A method in accordancewith claim 1 wherein the part is a motor end shield, said step ofproviding a mold comprising the step of providing an end shield moldfabricated from sand.
 3. A method in accordance with claim 1 wherein theinsert is a substantially circular steel insert ring, said step oforienting the insert comprises the step of orienting the substantiallycircular steel insert ring such that the substantially circular steelinsert ring contacts the second projections.
 4. A method in accordancewith claim 1 wherein said step of casting the part comprises the step ofcasting the part such that an inner diameter of the insert is exposedfrom the part after the part has been cast.
 5. A method in accordancewith claim 1 wherein said step of providing a mold comprises the step ofproviding a mold having three second projections extending from thefirst projection.
 6. A method in accordance with claim 1 wherein saidstep of casting the part comprises the step of casting the part withaluminum.
 7. A method in accordance with claim 1 further comprising thestep of machining an opening within the part to provide a smooth innersurface.
 8. A method in accordance with claim 1 further comprising thestep of machining a groove adjacent the insert.
 9. A method inaccordance with claim 8 further comprising surrounding the insert withthe grove.
 10. A method in accordance with claim 1 further comprisingplacing the insert on a top surface of the second projections.